424 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



2. V. THURETII Woronin, 1869, p. 157, PI. II, figs. 30-32 ; 

 Farlow, iSSi, p. 104; P. B.-A., No. 1029. Marine; filaments 

 varying considerably, but reaching So//.diatn.; antheridia ses- 

 sile, ovoid, 50-70 /A wide, 100-150 //, long; oogonia sessile or 

 oftener on short lateral branches, obovoid or pyriform, in- 

 clined, 200 /x wide, 250-300 /A long; oospores 150-180 ^ diam.; 

 aplanospores ovoid, 80X100-120 /a, on short branches at right 

 angles to the filaments. Me. to N. J. Europe. 



Forming dense dark green patches in muddy ditches by the 

 shore, probably extending farther south than the N. J. station. 

 The filaments of the American plant appear to be usually con- 

 siderably smaller than those described and figured by Woronin 

 for the European plant, sometimes as low as 30 /j., but otherwise 

 the> r agree. 



3. V. ORNITHOCEPHALA Agardh, 1817, p. 49; P. B.-A., 

 No. 984; V. scricea Walz, 1866, p. 150, PI. XIII, figs. 20 and 

 21 ; Wolie, 1887, p. 150, PI. CXXVII, figs. 12 and 13. Fila- 

 ments 35-45 M diam., oogonia 2-6-seriate, unilateral, obliquely 

 ovoid, 100-150 n diam., i}4 diam. long, opening through a 

 broad beak, sessile or very short-pedicelled and in form not un- 

 like a bird's head ; oospore nearly globose, about as wide as the 

 oogonium, but not filling it longitudinally, reddish when ripe, 

 with triple membrane; antheridia one or two at one end of a 

 series of oogonia, cylindric to subclavate, 20-25 /" diam., about 

 4 diam. long, bent nearly horizontally; zoospores 83-iooX 

 90-115^, in cylindrical or very slightly clavate sporangia; the 

 cilia much more closely set at the forward end. Occurs mostly 

 in running water. Mass., Pa. Europe. 



The seriate oogonia with their birds' heads facing the anther- 

 idium at one end, make a pretty good mark for distinguishing 

 this from species hitherto reported in America, but the same 

 characters are found in the European V. polysperma Hassall, 

 which very likely will sometime be found here. It is more 

 slender throughout, the filaments 22-33 //., the oogonia 60-65 P- 

 diam., and more nearly erect ; zoospores 66-88 //. diam.; anther- 

 idium always single. 



4. V. AVEKSA Hassall, 184^, p. 429 ; 1845., p. 54, PI. VI, 

 fig. 5; Walz, 1866, p. 151. PI. XIII, figs. 25 and 26; PI. XIV. 

 fig. 27 : Wolk-, 1887, p. 149, PI. CXXVII, figs. 5-8; P. B.-A., 

 Xo. 475. Filaments 60-100 ^ diam.; oogonia obliquely ovoid, 



^ile or shortly stipitate, two, rarely more in a series, the 

 beaks usually in opposite directions, mostly erect, 125X250 /A ; 



